cluster autoscaling on self hosted cluster

Possible, but not natively.

Cluster Autoscaler works the way it does because it can talk to the control plane of the cloud hosting the Cluster, like AWS, Azure, or GCP, and tells it to extend the cluster. The Cloud itself knows what it needs to do to extend the cluster, and so it makes the magic happen. If you were hosting your own cluster on your own hardware, it wouldn’t have the same ability to create additional VM’s for the cluster, unless you had additional integration features setup.